1. Field of the Invention
The present invention relates to a power semiconductor device widely used for a variety of purposes, which is, for example, mounted on a vehicle and used in FA equipment and an electric railway.
2. Description of the Background Art
A power semiconductor device houses power semiconductor elements and has a function of adjusting electric power by switching operations of the power semiconductor elements. This power semiconductor device is provided with a wiring line for the housed power semiconductor elements and the outside of the device.
As to the power semiconductor element housed in the conventional device, it is soldered to an insulating substrate, and a wiring line is formed by a wire or a metal lead from the insulating substrate or the element main body and is connected to a metal terminal guided outside the device.
The metal terminal is buried in a resin case of the device, and is guided outside the device from around the power semiconductor element. Alternatively, the metal terminal is connected to a wiring line on the insulating substrate positioned around the power semiconductor element and is guided outside the device. The device is filled with a resin so as to cover the insulating substrate, power semiconductor elements, metal wiring line and metal terminal, and is protected from the outside.
In contrast, there is a power semiconductor device in which a wiring line for a power semiconductor elements and the outside of the device is formed with a lead frame made of metal, and the wiring line using the lead frame is molded with a hard resin to be packaged (for example, see Japanese Patent Application Laid-Open No. 2004-165281). The wiring line is molded to be hardened, and then the essential spots of the lead frame thereof are subjected to cutting and bending, whereby the wiring line is provided to the device. Contrary to the device of the above-mentioned resin-filling type device, a lead frame in which metal leads have been lined in advance is used for manufacture in this case. Accordingly, in a case of mass production, this is put to practical use as the structure whose productivity is considerably high. Further, the wiring line is hardened with a hard resin, and thus the stress due to thermal expansion mismatching between the power semiconductor element and the other metal member whose thermal expansion differs from each other by a large amount can be dispersed. Therefore, the above-mentioned device is considerably useful for improving long-term reliability that has been highly valued.
In this power semiconductor device, the metal wiring line of a lead frame is formed around the power semiconductor elements and is guided outside the device from a portion other than above or below the portion in which the power semiconductor elements are mounted. This causes a problem that dead space is provided above or below the portion in which the power semiconductor devices are mounted, leading to a larger size of the power semiconductor device.
Further, there is conceivable a structure in which a metal terminal is bent to be formed in an upper portion of the device after the metal wiring line formed around the power semiconductor elements is guided outside the device. However, this causes such problems that a longer wiring line increases an inductance, and a larger lead frame reduces a material yield.